In general, an electronic device module is comprised of a board and one or more parts which are placed on the board and fixed to it. As a means of fixing these parts to the board, as in concrete examples which will be explained later, a fixing means of a type press-fitting a plurality of fixing pins provided integrally with the parts into corresponding through holes formed in the board is becoming the mainstream.
This fixing method using press fitting is a method of pushing a fixing pin into a through hole by a press fit connector press fitting device or the like with a considerable pressing force, the fixing pin has an outside shape dimension larger than the diameter of a through hole and partially has a resilient portion. A part can be tightly fixed to a board by a strong bonding force with a relatively simple and easy process.
This embodiment particularly relates to a repair method for detaching a part which is fixed to a board by the press fit process, from the board for repair or replacement of the part. Further, a repair jig for this purpose will be explained. Note that, as a known example relating to the embodiment, there is the following Patent Document 1.
In this Patent Document 1, it is disclosed to fasten a detachment use screw and make the screw itself act upon one of two objects which are engaged, bonded, or press fit with each other to thereby obtain a reaction force in the upward direction and to detach the two objects. For this reason, in a case where the force of engagement, bonding, or press fitting between these two objects is very high, the force by the fastened screw is applied directly to the parts, and thus there may be a possibility that the parts themselves or the board mounting the parts are damaged eventually.
On the other hand, the later explained embodiment is a process of fastening a screw through a detachment use block so as to obtain a force in an upward direction for one of the objects and detach it from the other object which is engaged, bonded, or press fit with the former object. This is different from the technique of the Patent Document 1. Note that, the Patent Document 1 relates to a socket itself and also a method of mounting the socket, which method is different from a process of detachment between two parts or two structures which are engaged, bonded, or press fit with each other as in the embodiment.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-26031
FIGS. 8A, 8B, and 8C are views illustrating a side view of a partial cross-section (A), a plan view (B), and a front view of a partial cross-section (C) of an electronic device module, as a first example, to which the embodiment is applied. This first example is a small-sized optical device which can be inserted or removed at the front surface of a communication apparatus. It has been developed as an SFP (Small Form Factor Pluggable) or XFP (10 Gigabit Small Form Factor Pluggable) optical transceiver and has come into wide use in recent years. This small-sized optical device can be replaced with another small-sized optical device having a different function, even after completion of a printed circuit board, and thus various desired functions can be realized on the same board.
In FIG. 8A, notation 1 is the above small-sized optical device. Various electronic circuits are formed in that device. A card connector 2 (see FIG. 8B, however, shown with front end portion 1b, in FIG. 8A, removed) for input/output signals, which is connected to these electronic circuits, is connected to a small-sized optical device engagement connector 3. This connector 3 is mounted on a printed circuit board 4 which is shown by a cross-section in FIG. 8A.
On this printed circuit board 4, the above small-sized optical device 1 can slide to the left and right in FIG. 8A, and thus the connector 2 can be freely attached to and detached from the connector 3. The insertion/removal directions of the small-sized optical device 1, in this case, is shown by the two-way arrows in FIGS. 8A and 8B. In FIG. 8B, the two 1a illustrate front surface portions, the 1a on the left side illustrates the position immediately before the small-sized optical device 1 is inserted into the deep position and immediately before the connector 2 is engaged with the connector 3, and the right side 1a illustrates the position in the middle of removal of the small-sized optical device 1 to the outside. Note that, the front surface portion 1a is shown in FIG. 8C. The small-sized optical device engagement connector 3, explained before, which is located in the deep position is illustrated by a dotted line.
When the small-sized optical device 1 is inserted and removed in the direction of the two-way arrows described above, the device 1 is guided by a cross-sectional box shaped cage 5 (see FIG. 8C). This cage 5 is provided with a plurality of fixing pins 6 at its bottom and is provided with an opening 5a for heat dissipation at its top. These fixing pins 6 are the press fit type pins explained above. These pins 6 have resilient parts 6a formed at parts of the pins 6. These pins 6 are pushed into through holes, formed in the printed circuit board 4, by a strong pushing force and tightly fix the cage 5 onto the printed circuit board 4. Note that, in the embodiments explained later, the “part” corresponds to that cage 5 and the “board” corresponds to that printed circuit board 4.
Incidentally, manufacturers of the above small-sized optical devices 1 are jointly establishing MSA (Multi Source Agreement) standards in which they determine specifications concerning the shapes of the parts 1, the shapes of the cages 5, the shapes of the small-sized optical device engagement connectors 3, and so on. Due to this, these are becoming a multivendor optical devices standard throughout the world.
The cage 5 must be able to withstand the mechanical stress at the time of insertion and removal of the small-sized optical device 1 in the cage 5. Therefore, it is difficult to make the device 1 as an SMD (Surface-Mounted Device). Further, even if making the device 1 as an IMD (insertion mounting device), since reflow of both surfaces of the printed circuit board 4 is becoming common practice, at the present time, this IMD cannot be employed from the point of view of workability. Therefore, the press fit process described above has become the mainstream.
Here, the process of press fitting the fixing pins 6 of the cage 5 into through holes in the printed circuit board 4 will be explained by using the drawings.
FIGS. 9A, 9B, and 9C are views illustrating the situation when fixing pins 6 of the cage 5, shown in FIGS. 8A, 8B, and 8C, are press fit in the through holes of the printed circuit board 4 with a cross-sectional side view (A), a plan view (B), and a cross-sectional front view (C), respectively.
In FIGS. 9A, 9B, and 9C, a press fit head 7 is placed on the cage 5. This head 7 is pressed downward (“pressing force”) to press fit the fixing pins 6, provided at the cage 5, into the through holes in the printed circuit board 4. At this time, a crush prevention block 8 is inserted inside the cage 5 in advance so that the cage 5 is not crushed by the press fit head 7. Further, in order to prevent excessive pressing by the press fit head 7, it is shaped such that the head 7 surrounds three sides of the cage 5.
FIGS. 10A, 10B, and 10C are views illustrating a partial cross-sectional side view (A), a plan view (B), and a partial cross-sectional front view (C) of an electronic device module of a second example, respectively, to which the embodiment is applied during a press fitting process.
The electronic device module of this second example is a sheet connector 10 and is provided with a large number of female type connectors 11. In a communication apparatus etc. which is comprised of a sub rack (shelf) structure, a sheet connector 10 is indispensable for connection with male type pins of a back wiring board (BWB) 13 in which a plurality of plug-in units (PIU) are accommodated as cards.
At the bottom of this sheet connector 10 as well, the already explained plurality of fixing pins 6 are provided. By pressing the connector 10 downward by the press fit head 12, resilient parts 6a of the fixing pins 6 are pressed into the through holes of the printed circuit board 4 and fixed.
Incidentally, regarding this sheet connector 10 as well, along with an increase in the ratio of SMD in the plug-in units (PIU), the two-surface reflow method has become the mainstream. For this reason, press fit type fixing pins are becoming the mainstream. This is because, if the IMD method is used, the production efficiency becomes poor since a manual soldering work must be carried out.
As previously explained, the theme of this embodiment resides in a repair method for detaching the cage 5, shown in FIGS. 8A to 8C and FIGS. 9A to 9C, from the printed circuit board 4 or a repair method for detaching the sheet connector 10, shown in FIGS. 10A to 10C, from the printed circuit board 4. Below, conventional examples of these repair methods will be explained.
FIGS. 11A and 11B are views illustrating a conventional example of the repair method by a side view of a partial cross-section (A) and a front view (B). Note that, the figures are shown taking as an example the electronic device units of FIGS. 8A to 8C and FIGS. 9A to 9C, but the principle of this repair method may be applied in the same way to the electronic device unit of FIGS. 10A to 10C, explained before, as well.
The electronic device unit shown in FIGS. 8A to 8C is turned upside down as shown in FIGS. 11A and 11B. Projecting parts 6b, i.e. the front ends of the fixing pins 6 which project from the back surface of the printed circuit board 4 are pressed by a repair use block 14 from above. By this, the entire cage 5 is pushed downward from the fixed board 4 to detach the cage 5 from the board 4. This is the conventional repair method.
In recent years, however, such a repair method according to the conventional art can no longer be applied. This is a problem. The reason for this is that, in FIGS. 11A and 11 B, the repair block 14 must push the entire cage 5 (or sheet connector 10) downward from the board 4 through the projecting parts 6b of the fixing pins 6. However, the projecting parts 6b are becoming to disappear due to various requests. This will be explained specifically below.
FIGS. 12A and 12B are views for explaining the problem of the conventional repair method for an electronic device unit (first example) with reference to a side view by the cross-section (A) and front view (B). In recent years, further higher density mounting of the above described SFPs and XFPs has been requested. For this reason, a structure arranging two sets of SFPs etc. so that their two surfaces face each other, was proposed as illustrated. In this way, it has become possible to improve the efficiency of housing SFPs in a communication apparatus.
However, when employing a two-surface facing structure as described above, the projecting parts 6b at the upper side of the cage 5 projecting from the back surface of the board 4 and the projecting parts 6b′ at a lower side of the cage 5′ projecting from the front surface of the board 4 become obstacles when making the two surfaces abut against each other, so these projecting parts were eliminated. As a result, a new repair method in place of the conventional repair method shown in FIGS. 11A and 11B has become necessary. The same is true for the electronic device module (second example) shown in FIGS. 10A to 10C as well. This will be shown by the drawings.
FIG. 13 is a side view of a partial cross-section for explaining the problem of the conventional repair method for an electronic device unit (second example). In a communication apparatus of a sub rack (shelf) structure explained above, along with the higher densities and higher speeds, the thickness of the board 4 has become greater. In particular, in BWB, as a recent tendency, a board comprised of 40 layers (sheet thickness: 6 mm) or more has appeared. Further, in order to handle high speed signals, noise countermeasures have become necessary.
In this regard, the projecting parts projecting from the back surface of the board 4, that is, the projecting parts 6b of the fixing pins 6 fixing the sheet connector 10, act as antennas and sometimes receive noise N. The noise N is transmitted to the BWB through the sheet connector 10 and ends up being transmitted to the PIU through an inner layer of the board 4, so there is possibility of the noise N causing malfunctions in the signal processing. As a result, the projecting parts 6b are cut away, and thus a new repair method in place of the conventional repair method shown in FIGS. 11A and 11B has become necessary.